Conversion of polymer lithium to polymer carboxylate

ABSTRACT

A carboxylate component is introduced into an alkali metal initiated polymer by means of a sequence in which an epoxy compound is reacted with the polymer followed directly by contact with a cyclic acid anhydride to produce a polymer composition having a carboxylate salt group. The resulting composition can then be hydrolyzed to produce carboxy-containing polymer which is useful in applications such as sheet molding compounds.

BACKGROUND OF THE INVENTION

This invention relates to carboxy terminated polymers.

Normally solid carboxy-containing polymers of conjugated dienes alone orcopolymerized with vinyl aromatic monomers have utility as modifiers inthermosetting polyester resin compositions as disclosed in U.S. Pat. No.4,020,036. These carboxy-containing polymers can be made by variety ofmethods as disclosed in the above patent. One method for making suchcarboxy-containing polymers is based on solution polymerizationtechniques wherein the monomers such as 1,3-butadiene and styrene arepolymerized in a solution with a hydrocarbyl lithium initiator underconditions such that a block copolymer of butadiene and styrene isformed. The polymerization mixture is then contacted with carbon dioxideto convert the polymerlithium to polymer-carboxy-lithium. The carbonatedreaction mixture can be further treated under hydrolysis conditions toconvert the carboxy-lithium end group to a carboxylic acid end groupduring polymer recovery operations.

While straightforward in theory, the carbonation procedure for preparingcarboxy-containing polymers has certain disadvantages. First, thecarbonation procedure requires a very high efficiency of mixing duringthe reaction of the polymerlithium in hydrocarbon solution with carbondioxide in order to achieve a high degree of carboxy content in thefinal polymer. Thus, expensive, specially constructed mixing equipmentis generally used for the carbonation step. Carbonation with CO₂ canalso be improved by using a large excess of CO₂ (>40 timesstoichiometric amount) and low reaction temperature (>25° C.). But theseconditions are not commercially attractive. Even under very good mixingconditions an appreciable portion of the polymer product does notcontain a carboxyl group because of a competing coupling reaction whichinvolves an intermediate polymer molecule containing a carboxy group orcarboxylate salt group. While the presence of the coupled product in thefinal polymer is not always deleterious it has been difficult to controlreproducibly the content of coupled polymer in the carboxy-containingpolymers made under the solution polymerization/carbonation process. Itis evident that as the coupled polymer content increases the carboxycontent of the polymer product will decrease. Thus, if the couplingreaction is difficult to control reproducibly, the carboxy content ofthe polymer produced under such conditions will also be difficult tocontrol.

It is desirable that the carboxy content of the carboxy-containingpolymers employed in thermosetting polyester resin compositions be ashigh as practicable and that the carboxy content be reproduciblyobtained in a process for making such carboxy-containing polymers.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a simplified method forproducing carboxy terminated polymer;

It is a further object of this invention to provide a method forproducing carboxy terminated polymer which is less dependent on vigorousmixing;

It is still a further object of this invention to provide a processgiving better reproducibility in production of carboxy terminatedpolymer;

It is still yet a further object of this invention to provide a higherdegree of carboxy incorporation; and

It is still yet a further object of this invention to provide a moreprecise control over coupling during carboxylation reactions.

In accordance with this invention, an alkali metal terminated polymer iscontacted with an epoxy compound and directly thereafter with a cyclicanhydride to produce a polymer carboxylate composition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Thus, it has now been found that a simple process can be employed forthe production of carboxy-containing polymers utilizing the solutionpolymerization process but which does not require expensive mixingequipment and meticulous control of the mixing step or excess reagent(CO₂) and low reaction temperature as in the carbonation procedure.Moreover, this simple process provides carboxy-containing polymers whichcan be reproducibly made to a very high content of the carboxy groupwith substantially no coupled polymer being produced. However, ifcoupled polymer is desired the inventive process of this invention canbe employed to reproducibly make polymer having the desired level ofcoupled product in the carboxy-containing polymer product.

The invention process employs first contacting a polymer-alkali metalcomposition with an epoxy compound (oxirane compound) in order toconvert the polymer metal to a polymer oxy-metal intermediate product.In the second step of the inventive process, the thus-formedintermediate product is thereafter directly contacted with a cyclic acidanhydride still under solution conditions to produce a polymercomposition having a carboxylate salt group present on the polymerchain. By "directly contacted" is meant that there is no intermediatehydrolysis step. Generally, the anhydride will be reacted immediatelyafter the first reaction but this is not essential so long as nohydrolysis is carried out prior to adding the anhydride. Said polymershaving the carboxylate salt group can then be hydrolyzed if so desiredduring conventional isolation procedures to provide carboxy-containingpolymers which can be utilized in thermosetting resin compositions aswell as in other applications.

It should be noted that the prior art discloses the reaction of polymermetal with epoxy compounds to produce polymer oxy-metal species. It isfurther known that such materials can be hydrolyzed to form polymerscontaining hydroxyl groups. Said polymers which contain hydroxyl groupsare known to react with cyclic acid anhydrides to form polymericmaterials containing carboxy groups. This latter reaction is disclosedin U.S. Pat. No. 4,020,036 in column 3 lines 11-18. A similar disclosureis found in U.S. Pat. No. 3,308,170 at column 3 lines 55-69 and column 4lines 52-69. Contrary to the teachings of these patents the instantinvention employs no intermediate hydrolysis step after the formation ofthe polymer oxy-metal from polymer metal and the epoxy compound.Surprisingly it has been found that the omission of the hydrolysis stepat this stage provides a very high carboxy content in the final productwhen compared to the typical carbonation procedure for producingcarboxy-containing polymers. Moreover, it has been found that the use ofan intermediate hydrolysis step as taught by the prior art but withoutisolation of the produced hydroxy-containing polymer provides a very lowyield of carboxy-containing polymer when the intermediate hydrolyzedmixture is reacted with the cyclic acid anhydride at relatively hightemperatures (110°-120° C.).

The polymerization procedure to produce the block polymers is broadlyknown as disclosed in Zelinski et al, Rubber Chemistry and Technology,41 161-181, (1968), particularly pages 162 to 166, the disclosure ofwhich is hereby incorporated by reference. The initiator is preferablyan organolithium such as n-butyllithium as disclosed in British Pat. No.895,980, the disclosure of which is hereby incorporated by reference butcan be any organoalkali metal initiator as disclosed in Hsieh, U.S. Pat.No. 3,175,997 (Mar. 30, 1965), the disclosure of which is herebyincorporated by reference. Similarly, the monomers disclosed in saidHsieh patent are applicable to the polymers used in the invention. Forexample, suitable monomers include conjugated dienes having 4 to 12,preferably 4 to 8 carbon atoms per molecule such as 1,3-butadiene andisoprene, and monovinyl-substituted aromatic compounds having from 8 to18 carbon atoms per molecule such as styrene. Preferably, the polymersare copolymers produced by sequential addition of the monomers. Morespecifically, the invention is applicable to the production of carboxyterminated rubber, i.e., compositions having at least 50 weight percentof the conjugated diene such as 1,3-butadiene, preferably 90 to 80weight percent diene, such as 1,3-butadiene, and 10 to 20 weight percentof monovinyl-substituted aromatic compound such as styrene. Withcopolymers the order of addition is generally such that the alkali metalis on the diene, however, the reverse order is possible also.

The reaction, as an example of the invention, can be graphicallydepicted by the following reaction: ##STR1##

The epoxy compounds which can be employed to react with polymer-lithiumin the first step of the inventive process can be defined by the generalformula shown below ##STR2## wherein each R and each R' is selected fromthe group consisting of hydrogen, alkyl, aryl, alkaryl, aralkyl andcycloalkyl radicals and one R and one R' can together form an alkyleneradical. The epoxy compounds have from 2 to 30 carbon atoms permolecule.

The epoxy compound can be selected from a large group of suitablecompounds such as ethylene oxide (oxirane), propylene oxide,1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxy-3-methylbutane,2,3-epoxy-3-methylbutane, 1,2-epoxy-2,4,4-trimethylpentane,1,2-epoxycyclohexane, 1,2-epoxycyclooctane,1,2-epoxy-4-cyclohexylpentane, 1,2-epoxyoctadecane, 1,2-epoxyeicosane,styrene oxide, 1,2-epoxytriacontane, 1,2-epoxy-2-cyclohexylbutane,3,4-epoxy-3,4-diethylhexane, 1,2-epoxy-2-(para-tolyl)butane,2,3-epoxy-3-methyl-2-benzylpentane, and the like.

Suitable cyclic acid anhydrides which are reacted with the polymeroxy-lithium according to the instant invention can be represented by thegeneral formula shown below: ##STR3## wherein R" is a divalenthydrocarbyl radical of 2-14 carbon atoms. For ease of handling andmixing efficiency in the reaction of the cyclic acid anhydride with thepolymer oxy-lithium it is preferred that the cyclic acid anhydride be atleast partially soluble in hydrocarbon solvents such as the paraffinichydrocarbons or cycloparaffinic hydrocarbons, e.g. cyclohexane. Examplesof suitable cyclic acid anhydride compounds include maleic anhydride,succinic anhydride, glutaric anhydride, phthalic anhydride,3-methylphthalic anhydride, 4-methylphthalic anhydride,cis-hexahydrophthalic anhydride, trans-hexahydrophthalic anhydride,hexahydro-4-methylphthalic anhydride, cis-1,2,3,6-tetrahydrophthalicanhydride, citraconic anhydride, dl-camphoric anhydride,3-methylglutaric anhydride, methylsuccinic anhydride,2-dodecen-1-ylsuccinic anhydride and the like.

The amount of epoxy compound to be added in Step One in the reactionwith the polymer metal can be conveniently expressed in terms of themolar ratio of epoxy compound to the polymer metal. For maximum carboxycontent in the final product the molar ratio of epoxy compound topolymer metal should be at least 1/1. Molar ratios below 1/1 willproduce coupled product in the carboxy-containing polymer. Obviously, ifcoupled product is desired in the final product one can employ ratiosbelow 1/1 as indicated. Broadly the the molar ratio of epoxy compound topolymer metal can be from 0.1/1 up to 5/1 and preferably from 0.8/1 to2/1. It is believed epoxy compound in excess of the stoichiometricamount 1/1 to convert polymer metal to polymer oxy-metal will not besignificantly harmful to the process in terms of the second stepreaction.

The temperature employed for the reaction of the epoxy compound withpolymer metal can be broadly from 30°-200° C. and preferably from80°-120° C., more preferably 100°-120° C.

The time employed in the reaction of the epoxy compound with polymermetal is not critical because of the extreme speed of this reaction inthe temperature ranges disclosed above. Although the time might bedependent to some extent on the mixing efficiency for the epoxy compoundin the polymer metal, suitable times within the range 10 seconds up to10 minutes can be employed for this reaction step.

The pressure employed for the reaction of the epoxy compound and polymermetal is not believed to be critical and one can employ the autogenouspressure of the system as a matter of convenience. For those epoxycompounds which are relatively volatile it is preferred that thereaction be conducted under the pressure of an inert gas such asnitrogen, helium or argon in order to aid in keeping the epoxy compoundin the reaction mixture solution.

In the second step of the instant invention a cyclic acid anhydride isadded to the reaction mixture which is obtained from Step One, i.e. thereaction of the epoxy compound with polymer metal to make polymeroxy-metal. This reaction mixture can be treated with the cyclic acidanhydride employing molar ratios of anhydride to starting polymer metalthat are the same as the earlier disclosed ratios of epoxy compound topolymerlithium. Thus a molar ratio of cyclic acid anhydride to polymermetal of 0.1/1 to 5/1 can be broadly employed while preferably the ratiois from 0.8/1 to 2/1.

The temperature employed for the reaction in Step Two can be also thethe same as for Step One for both the broad and preferred ranges.

Again the time employed for the reaction is not believed especiallycritical and the same range can be employed in this step as disclosedfor the first step. However, if a cyclic acid anhydride is employedwhich has low solubility in the reaction mixture additional time can beemployed to aid in completing the reaction of the cyclic acid anhydridewith the polymer oxy-metal.

The pressure employed in Step Two is not believed to be critical to thepractice of this invention.

Following the reaction of the cyclic acid anhydride with the polymeroxy-metal in Step Two of the inventive process the reaction mixture canbe treated in a variety of conventional techniques in order to recoverthe carboxy-containing polymer or even a carboxylate salt if so desired.As noted above the instant invention process is particularly suited tobe used with solution polymerization processes which are conducted inthe presence of hydrocarbon solvents or diluents. The final reactionmixture thus will be a hydrocarbon solution or dispersion of the polymercarboxylate salt. This polymeric solution or dispersion can beconveniently handled by steam stripping techniques which are well knownin the art of solution polymerization for recovering polymers fromhydrocarbon solvents. During the steam stripping procedure thecarboxylate salt may be substantially converted to the polymercarboxylic acid material. If appreciable metal ions are present duringthe steam stripping operation it is possible that another carboxylatesalt may be formed and recovered in the steam stripping procedure.Another well known procedure for recovering polymers from hydrocarbonsolutions is to add a nonsolvent for the polymer such as alcohols,water, and the like to the hydrocarbon solution thus precipitating orcoagulating the polymer. If the the precipitation or coagulation iscarried out in the presence of a mineral acid the carboxy-containingpolymer will result. If no acidic compound is present then there may berecovered the carboxylate salt of the polymer material.

The by weight percentage of polymer produced having carboxy attachedthereto can be quite high, for instance 40 to 99 percent or moregenerally 60 to 95 percent. Preferably at least 75 percent is produced.

Antioxidants and/or other polymer stabilizers may be added during thepolymer recovery step as is known in the art.

In the examples that follow the method employed for determining theweight percent polymer with carboxy end groups is described as follows.The determination is for the weight percent polymer with carboxy endsnot the weight percent carboxy content.

The rubber is dissolved, an internal standard added, and thenchromatographed on columns that pass the carboxy polymer and again oncolumns that retain the carboxy polymer. The areas of the product peaksare measured relative to the internal standard and the weight percentcarboxy polymer is calculated. The apparatus and reagents are asfollows:

1. Standard solution--polystyrene 20,000±5,000 molecular weightdissolved (0.006 g/mL) in chloroform.

2. Solvents--tetrahydrofuran, methanol, chloroform (HPLC grade made byFisher Scientific).

3. Gel permeation chromatograph with a UV detector and a switching valveto two sets of columns. One set of columns must be DuPont size exclusioncolumns (SEC) to retain carboxy ended polymer; i.e.,60-100-500-1000-1000 worked well. The other set should be micro styrageltype or non-functional SEC type columns to chromatograph the totalpolymer, i.e., three 500 SEC columns.

The procedure is as follows:

1. The SEC columns are "activated" to hold the carboxy ended polymer bypumping methanol for 30 minutes and then chloroform until a steady baseline is obtained, 30-60 minutes. Columns must be "reactivated" withmethanol after 6 to 10 samples are run.

2. Polymer solution (18% in cyclohexane), 2 mL, is mixed with internalstandard solution, 3.5 mL.

3. Add 0.6 mL of the step B 2 mixture to 20 mL of THF and chromatographon the THF microstyragel columns for total polymer.

4. Add 0.6 mL of the step 2 mixture to 20 mL of chloroform andchromatograph on the SEC columns with CHCl₃ carrier. This holds thecarboxy polymer on the packing, allowing the amount of non-functionalpolymer to be measured.

The equation for calculating percent carboxy polymer is as follows:##EQU1## where A is the area under the first peak (product) of thecarboxylated polymer purged through THF columns, B is the area under thesecond (standard) peak for carboxylated polymer passed through THFcolumns, C is the area under the first (product) peak of thecarboxylated polymers retained chloroform columns and D is the areaunder the second (standard) peak of the carboxylated polymer retainedchloroform columns.

Care must be taken not to get any THF in the chloroform sample or intothe chloroform columns or the carboxy polymer will bleed out and percentcarboxy polymer calculations will be low.

EXAMPLE I (CONTROL)

A series of runs was conducted using a 0.5 gallon Chemco reactor wherein(85/15) butadiene/styrene block copolymers were prepared in cyclohexanesolution with n-butyllithium initiator. The active polymerlithiummixtures were reacted with ethylene oxide and the polymer oxy-lithiummixtures then treated with several different hydrolysis reagents (aq.HCl, aq. acetic acid, and H₂ O) to convert polymer-OLi to polymer-OH.The mixtures were then reacted with hexahydro-4-methylphthalicanhydride. Polymer samples were obtained at various reaction times fromthis final mixture and analyzed for carboxy content.

The polymerization recipe, conditions and details of the reactions arepresented below. The results obtained are presented in Table I.

    ______________________________________                                                                 Polymeri-                                                                     zation                                                                        Recipe                                               ______________________________________                                        Cyclohexane, g             650                                                Tetrahydrofuran.sup.(a), g 0.05                                               Styrene, g                 15                                                 n-Butyllithium.sup.(b), mhm.sup.(c)                                                                      1.2.sup.(d)                                        (Polymerize 15 min. at 70° C.)                                         1,3-Butadiene, g           85                                                 (Polymerize 5-7 min. to peak temperature of 110° C.)                   Ethylene oxide.sup.(e), mhm                                                                              1.0                                                (React 5 min.)                                                                Hydrolysis Reagent         variable                                           (React 5 min. at 110° C.)                                              H--4-MPA.sup.(f), mhm      2.0                                                (React at 100° C., sample at indicated intervals for carboxy           group                                                                         analysis)                                                                     ______________________________________                                         .sup.(a) Charged as a so1ution of THF in cyclohexane, 0.01 g per mL.          .sup.(b) Charged as a 0.262 M solution in heptane/cyclohexane mixture.        .sup.(c) mhm = gram millimoles per 100 g of total monomers.                   .sup.(d) Estimated 0.2 mhm for scavenger level and 1.0 mhm as effective       initiator level.                                                              .sup.(e) Charged as 0.5 M solution in cyclohexane.                            .sup.(f) H--4MPA = hexahydro4-methylphthalic anhydride charged as 0.5 M       solution in cyclohexane.                                                 

                  TABLE I                                                         ______________________________________                                                                Reaction                                              Run                     Time,                                                 No.   Hydrolysis Reagent, mhm                                                                         min.      Carboxy %                                   ______________________________________                                        1     12.0 M HCl,   2.0     20      -2.6.sup.(a)                                                          60      -0.3                                      2     17.4 M Acetic Acid,                                                                         2.0     20      5.8                                                                   60      3.6                                       3     H.sub.2 O.sup.(b),                                                                          1.0     20       --.sup.(c)                                                           60      -0.8                                      ______________________________________                                         .sup.(a) A negative value indicates no detectable carboxy content.            .sup.(b) Charged as a solution in THF, 0.01 g/mL.                             .sup.(c) A dash-- indicates not determined.                              

The results in Table I show that conditions which should have beeneffective to convert polymer-OLi to polymer-OH prior to reaction withthe cyclic acid anhydride were certainly not conducive to the productionof polymers having a high carboxy content, only about 4-6% beingobtained at best under the conditions employed.

EXAMPLE II

A run was made according to this invention in the 0.5 gallon Chemcoreactor wherein polymer-OLi was reacted directly with H-4-MPA, i.e.,without an intermediate step to hydrolyze polymer-OLi to polymer-OH. Thepolymerization recipe is shown below and the results are shown in TableII.

    ______________________________________                                                              Polymerization                                                                Recipe                                                  ______________________________________                                        Cyclohexane, g          650                                                   THF, g (0.01 g/mL in cyclohexane)                                                                     0.07                                                  Styrene, g              15                                                    n-BuLi, mhm (0.25 M solution in                                                                       1.03                                                  heptane/cyclohexane mixture, 0.10                                             mhm scavenger level)                                                          (Polymerize for 10 min. at 70° C.)                                     1,3-Butadiene, g        85                                                    (Polymerize 3-5 min. to peak of 105° C.)                               Ethylene oxide, mhm (0.5 M in cyclohexane)                                                            1.2                                                   (React 3-5 min. at 105° C.)                                            H--4-MPA, mhm (0.4 M in cyclohexane)                                                                  1.2                                                   ______________________________________                                    

React at 100°-105° C. for indicated time and samples withdrawn forcarboxy content analysis. BHT (antioxidant) was added to each sample ata level of 1 phr.

                  TABLE II                                                        ______________________________________                                                      Reaction Carboxy                                                Run           Time,    Content                                                No.           Min.     %                                                      ______________________________________                                        1               0.sup.(a)                                                                            -2.05                                                  2             5        84.4                                                   3             10       86.9                                                   ______________________________________                                         .sup.(a) Sampled prior to addition of H--4MPA.                           

The results in Table II show that the inventive method provides polymerswith a very high carboxy content.

EXAMPLE III

Additional runs were made according to the invention in a 2 gallonChemco reactor to prepare large samples of carboxy-containing polymerfor evaluation in thermosetting unsaturated polyester resin composition.The polymerization recipe is shown below and the results are presentedin Table III.

    ______________________________________                                                              Polymerization                                                                Recipe                                                  ______________________________________                                        Cyclohexane, g          3,900                                                 THF, g (0.01 g/mL in cyclohexane)                                                                     0.42                                                  Styrene, g              90                                                    n-BuLi, mhm             0.88-1.00                                             (0.517 M in heptane/cyclohexane mixture,                                      0.15 mhm scavenger level)                                                     (Polymerize 10 min. at 70° C., cool to 60° C.)                  1,3-Butadiene, g        510                                                   (Polymerize to peak temperature of 110° C.)                            Ethylene oxide (0.5 M in cyclohexane)                                                                 1.2                                                   (React 2 min.)                                                                H--4-MPA, mhm (0.4 M in cyclohexane)                                                                  1.2                                                   (React 5 min., cool to 70° C.)                                         BHT (antioxidant), g    2.4                                                   ______________________________________                                    

Polymer was recovered by steam stripping using the following recipecharged to the stripper.

    ______________________________________                                        Polymer solution, g                                                                            2,600                                                        CaCl.sub.2, g    0.54                                                         Tamol, g         0.37                                                         Water, gallons   3.3                                                          ______________________________________                                    

It was noted that Tamol (dispersant) was not necessary to provide crumbformation in the steam stripping operation.

Batches from individual polymerization runs were combined to provide twopolymers which differed primarily only in molecular weight.

                  TABLE III                                                       ______________________________________                                        Unsatura-                                                                     tion.sup.(a), %                                                                            Styrene, %             Carboxy                                   Poly-         Vi-           To-             Content                           mer   Trans   nyl    Block.sup.(b)                                                                        tal.sup.(c)                                                                        HI.sup.(d)                                                                         I.V..sup.(e)                                                                        %                                 ______________________________________                                        A     50.0    12.2   13.5   14.4 1.05 1.16  82.7                              B     49.2    12.2   14.4   14.2 1.07 1.05  82.4                              ______________________________________                                         .sup.(a) Normalized values, based on butadiene portion of the polymer, as     determined by infrared spectra analysis.                                      .sup.(b) Determined by oxidative degradation.                                 .sup.(c) Determined by ultraviolet spectra anlysis.                           .sup.(d) HI = heterogeneity index, ratio of wt. average molecular weight      to number average molecular weight (Mw/Mn).                                   .sup.(e) I.V. = inherent viscosity determined in toluene. Each polymer wa     gel free.                                                                

Polymer A was evaluated in a thermosetting unsaturated polyester resincomposition in a system similar to that in the Example of U.S. Pat. No.4,020,036, the disclosure of which patent is hereby incorporated byreference. Polymer A was found to be entirely suitable for saidapplication. Polymer B, while also suitable for this application, didnot give as good results in terms of appearance aspects of the moldings.

EXAMPLE IV

Since the carboxy group in the polymers made according to the instantinvention is apparently also accompanied by an ester group by virtue ofthe opening of the cyclic acid anhydride, it was desirable to test thestability of the ester group toward polymer treatment procedures.

A portion of polymer A (Example III) as water wet crumb from the steamstripping recovery step was charged to an internal mixing device (MidgetBanbury). The polymer was mixed at 165°-175° C. and samples removed atdifferent times to determine carboxy content. Results of this test arepresented in Table IV.

                  TABLE IV                                                        ______________________________________                                        Sample       Mixing     Carboxy                                               No.          Time, min. Content, %                                            ______________________________________                                        1            1              90.9.sup.a                                        2            5              88.3.sup.a                                        3            10             84.3.sup.a                                        4            11             79.8.sup.b                                        5            15             64.6.sup.b                                        6            20             54.5.sup.b                                        7            25             46.3.sup.b                                        8            0     (control)                                                                              86.8                                              ______________________________________                                         .sup.a Banbury only partially filled.                                         .sup.b Banbury filled.                                                   

The results in Table IV show that under the severe conditions of highshear mixing at high temperature for an extended period the carboxycontent was reduced about 50%. However, it should be noted that typicalresidence times for an extruder drying operation or a pelletizingextruder for such polymers is on the order of 1-3 minutes. Under suchconditions very little loss of carboxy content would be expected due tothe cleavage of the polymer-ester linkage.

EXAMPLE V

Other runs were made according to this invention in which propyleneoxide and ethylene oxide were compared in the first step of theinventive process. A control run was also included in this series whichemployed CO₂ in place of the cyclic acid anhydride in the second step ofthe process. The polymerization recipe is shown below and the resultsobtained are provided in Table V.

    ______________________________________                                                            Polymerization - Recipe                                   ______________________________________                                        Cyclohexane, g        650                                                     Styrene, g            15                                                      THF.sup.(a), g        0.07                                                    n-BuLi.sup.(b), mhm   variable                                                (Polymerize at 70° C. for 10 min.)                                     1,3-Butadiene, g      85                                                      (Polymerize about 7 min. to peak                                              temperature 110° C.)                                                   Propylene oxide (PO).sup.(c) or                                                                     variable                                                Ethylene oxide (EO).sup.(c), mhm                                              (React 3-5 min.)                                                              H--4-MPA.sup.(c) or CO.sub.2                                                                        variable                                                (React 3-5 min. except Runs 5 and 6)                                          Sample and add BHT, g 0.4                                                     ______________________________________                                         .sup.(a) Charged as a solution in cyclohexane 0.01/g per mL.                  .sup.(b) Charged as a 0.265 M solution in heptane/cyclohexane mixture.        Scavenger level estimated at 0.20 mhm.                                        .sup.(c) Charged as 0.5 M solution in cyclohexane.                       

                  TABLE V                                                         ______________________________________                                                            Polymer                                                   Run   n-BuLi  PO     EO   H--4-MPA                                                                              Carboxy,                                                                             Coupled.sup.(a)                      No.   mhm     mhm    mhm  mhm     %      %                                    ______________________________________                                        1     1.08    0.88   --   0.88    58     5.5                                  2     1.20    0.55   --   1.00    54     26                                   3     1.08    --     0.88 0.88    83     2.0                                  4     1.20    --     0.55 1.00    45     34                                   5     1.08    0.88   --   0.88    55.4   --                                   (Samples taken at 0.5, 3.5 7.5                                                                      64.8     --                                             12.5 and 20 min. after H--4-MPA                                                                     67.0     --                                             addition)             66.0     --                                             6.sup.(b)                                                                           1.08    --     0.88 --      9.6    --                                   ______________________________________                                         .sup.(a) Percent of polymer chains that have coupled during the reaction      sequence as determined by gel permeation chromatography using THF as          solvent.                                                                      .sup.(b) Run made using CO.sub.2 instead of H--4MPA by charging CO.sub.2      at 50 psig and maintaining this pressure until no more is consumed.      

The results in Table V show that ethylene oxide gave better results thanpropylene oxide in terms of polymer carboxy content (Runs 1 and 3). Itis also seen that molar ratios of epxoy compound to polymer metal(effective n-BuLi level) less than 1/1 can give rise to increasedcoupled product and decreased carboxy content (Runs 1 and 2; 3 and 4).Run 5 shows that the reaction of polymer-OLi with H-4-MPA is essentiallycomplete in about 4 minutes under the conditions employed. Control Run 6shows that use of CO₂ in place of a cyclic acid anhydride (H-4-MPA) didnot give polymer product with a high carboxy content.

EXAMPLE VI

Runs were made in a 0.5 gallon Chemco reactor according to the inventionto evaluate methods of treating propylene oxide prior to use in Step Oneof the inventive process. In addition, phthalic anhydride was used asthe cyclic acid anhydride in one run of the series. The polymerizationrecipe is shown below and the results are presented in Table VI.

    ______________________________________                                                          Polymerization Recipe                                       ______________________________________                                        Cyclohexane, g      650                                                       Styrene, g          15                                                        THF.sup.(a), g      0.07                                                      n-Buli.sup.(b), mhm 1.38                                                      (Polymerize 10 min. at 70° C.)                                         1,3-Butadiene, g    85                                                        (Polymerize several min. to peak                                              temperature of 100-110° C.)                                            Propylene oxide (PO) or                                                                           variable                                                  Ethylene oxide (EO)                                                           (React 3-5 minutes)                                                           H--4-MPA, except Run 9                                                                            variable                                                  (React 3-5 minutes)                                                           ______________________________________                                         .sup.(a) Charged as solution in cyclohexane, 0.01 g/mL.                       .sup.(b) Charged as 0.28 M solution in heptane/cyclohexane mixture.           Scavenger level was estimated at 0.5 mhm.                                

                  TABLE VI                                                        ______________________________________                                                           Polymer                                                                                   Carboxy                                        Run   PO      EO       H--4-MPA                                                                              Content,                                                                             Coupled,                                No.   mhm     mhm      mhm     %      %                                       ______________________________________                                        1     --      0.88.sup.(a)                                                                           0.88    69.1   --                                      2     0.88.sup.(a)                                                                          --       0.88    50.2   --                                      3     1.76.sup.(a)                                                                          --       0.88    73.6   --                                      4     0.88.sup.(b)                                                                          --       0.88    61.5   --                                      5     0.88.sup.(c)                                                                          --       0.88    28.6   --                                      6     --      1.76.sup.(a)                                                                           1.76    97.0   --                                      7     1.76.sup.(b)                                                                          --       1.76    90.5   --                                      8     1.76.sup.(b)                                                                          --       1.76    85.4   --                                      9     --      1.76.sup.(a)                                                                           1.76 (PA).sup.(d)                                                                     42.7   23                                      ______________________________________                                         .sup.(a) Untreated.                                                           .sup.(b) Treated over type 5A molecular sieves.                               .sup.(c) Treated over Kaiser A201 activated alumina.                          .sup.(d) PA = phthalic anhydride, charged as 0.343 M solution in THF.    

The results in Table VI show treatment of propylene oxide over activatedalumina was not helpful but that treatment over molecular sieves washelpful in terms of carboxy content of the final product. Untreatedethylene oxide still gave slightly better results than propylene oxidetreated with molecular sieves. It is also seen again that molar ratiosof epoxy compound to effective n-BuLi (polymerlithium) of greater than1/1 were effective in giving high levels of carboxy content in thepolymer. Run 9 shows that phthalic anhydride can be employed as thecyclic acid anhydride according to the process of this inventionalthough the results were not outstanding in terms of carboxy content.

EXAMPLE VII

Control runs were made in the 0.5 gallon Chemco reactor to determine theeffect of omitting Step One from the sequence of the invention process.The polymerization recipe is shown below and the results are provided inTable VII.

    ______________________________________                                                            Polymerization Recipe                                     ______________________________________                                        Cyclohexane, g        975                                                     Styrene, g            19.5                                                    THF.sup.(a), g        0.105                                                   n-Buli.sup.(b), mhm effective                                                                       1.0                                                     (Polymerize 15 min. at 70° C.)                                         1,3-Butadiene, g      127.5                                                   Styrene, g            3.0                                                     (Polymerize about 10 min. to 100-110° C.)                              H--4-MPA.sup.(c) or   variable                                                citraconic anhydride.sup.(d), mhm                                             (React several minutes, recover polymer)                                      ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                                         Polymer                                                                             Carboxy                                                Run                    Content, Coupled,                                      No.      Anhydride, (mhm)                                                                            %        %                                             ______________________________________                                        1        H--4-MPA (4)  29.6     46                                            2        citraconic (11.4)                                                                           28.1     75                                            ______________________________________                                         .sup.(a) Charged as solution in cyclohexane of 0.01 g/mL.                     .sup.(b) Charged as 0.435 M solution in heptane/cyclohexane mixture.          .sup.(c) Charged as 0.4 M solution in cyclohexane.                            .sup.(d) Charged as the neat compound. The compound did not appear to be      very soluble in cyclohexane (reaction mixture).                          

The results in Table VII show that the omission of the epoxy compoundreaction with polymerlithium before the addition of the cyclic acidanhydride does not provide as high a yield of carboxy content in thepolymer product but does show a relatively high degree of coupledpolymer.

EXAMPLE VIII

Scaled up polymerization reactions were utilized to prepare about 100 kgof carboxy containing polymer made according to the invention. Thepolymerization recipe and reaction sequence was substantially the sameas that shown below.

    ______________________________________                                        Polymerization Recipe                                                                                 Parts by wt.                                          ______________________________________                                        Solvent                   650                                                 THF                       0.07                                                Styrene                   15                                                  n-BuLi                    0.082                                               (0.026 scavenger level, 0.056 effective)                                      (Polymerize about 10 min. initiated at 50-60° C.)                      1,3-Butadiene             85                                                  (Polymerize to peak temperature of 100-110° C.)                        Ethylene Oxide (at peak temp.)                                                                          0.039                                               (React 2 min.)                                                                H--4-MPA                  0.15                                                (React at least 0.5 min., flash solvent, discharge                            to blend tank)                                                                BHT                       0.40                                                ______________________________________                                    

In the recipe shown above the molar ratio of ethylene oxide topolymerlithium (effective n-BuLi) is 1/1 and the molar ratio of H-4-MPAto polymerlithium is also 1/1. These ratios were employed in order toreduce the possibility that unreacted ethylene oxide or H-4-MPA would bepresent and perhaps carried over with the flashed solvent to recyclestreams.

The polymer had the properties shown below:

    ______________________________________                                        Normalized unsaturation                                                       % Trans              40.2                                                     % Vinyl              10.1                                                     Total styrene, %     13.5                                                     Block polystyrene, % 13.2                                                     Mw/Mn × 10.sup.-3                                                                            109/101                                                  Heterogeneity index  1.07                                                     Inherent viscosity   1.15                                                     325 mesh gel, %      0                                                        Carboxy content, %   74                                                       Coupled polymer, %   <2                                                       Viscosity of 30 wt. % solution                                                                     31,700                                                   in Styrene at 25° C., cP                                               ______________________________________                                    

This polymer was evaluated in a thermosetting polyester sheet moldingcomposition in a system similar to that of the Example of U.S. Pat. No.4,020,036. This polymer evaluation demonstrated that the product wasentirely satisfactory as an additive for the unsaturated polyester sheetmolding composition.

While this invention has been described in detail for the purpose ofillustration, it is not to be construed as limited thereby but isintended to cover all changes and modifications within the spirit andscope thereof.

I claim:
 1. A polymerization process comprising:introducing anorganolithium initiator into a reaction zone containing a hydrocarbonsolvent; introducing a conjugated diene monomer having 4 to 8 carbonatoms per molecule into said reaction zone and carrying outpolymerization; thereafter introducing an epoxy compound and mixing theresulting ingredients at a temperature of 30° to 200° C., said epoxycompound having the formula ##STR4## wherein each R and each R' isselected from the group consisting of hydrogen, alkyl, aryl, alkaryl,aralkyl and cycloalkyl radicals and one R and one R' can together forman alkylene radical; thereafter directly contacting the thus formedintermediate with a cyclic acid anhydride and mixing at a temperature of30° to 200° C., said cyclic acid anhydride having the formula ##STR5##wherein R" is a divalent hydrocarbyl radical of 2 to 14 carbon atoms;subjecting the resulting composition to steam stripping or precipitationin the presence of an acid, to produce a carboxy containing rubberypolymer.
 2. A method according to claim 1 wherein said conjugated dieneand a monovinyl substituted aromatic compound are sequentiallyintroduced into said solvent and wherein said resulting composition issubjected to steam stripping.
 3. A process according to claim 2 whereinsaid epoxy compound is selected from ethylene oxide, propylene oxide,1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxy-3-methylbutane,2,3-epoxy-3-methylbutane, 1,2-epoxy-2,4,4-trimethylpentane,1,2-epoxycyclohexane, 1,2-epoxycyclooctane,1,2-epoxy-4-cyclohexylpentane, 1,2-epoxyoctadecane, 1,2-epoxyeicosane,styrene oxide, 1,2-epoxytriacontane, 1,2-epoxy-2-cyclohexylbutane,3,4-epoxy-3,4-diethylhexane, 1,2-epoxy-2-(para-tolyl)butane, and2,3-epoxy-3-methyl-2-benzylpentane.
 4. A method according to claim 2wherein said cyclic acid anhydride is selected from maleic anhydride,succinic anhydride, glutaric anhydride, phthalic anhydride,3-methylphthalic anhyride, 4-methylphthalic anhydride,cis-hexahydrophthalic anhydride, trans-hexahydrophthalic anhydride,hexahydro-4-methylphthalic anhydride, cis-1,2,3,6-tetrahydrophthalicanhydride, citraconic anhydride, dl-camphoric anhydride,3-methylglutaric anhydride, methylsuccinic anhydride, and2-dodecen-1-ylsuccinic anhydride.
 5. A method according to claim 2wherein said organolithium compound is n-butyllithium.
 6. A methodaccording to claim 2 wherein said monovinyl substituted aromaticcompound is styrene.
 7. A method according to claim 2 wherein saidconjugated diene is selected from 1,3-butadiene and isoprene.
 8. Amethod according to claim 2 wherein said hydrocarbon solvent iscyclohexane.
 9. A method according to claim 2 wherein said epoxycompound is selected from ethylene oxide, propylene oxide,1,2-epoxybutane, 1,2-epoxypentane, 1,2-epoxy-3-methylbutane,2,3-epoxy-3-methylbutane, 1,2-epoxy-2,4,4-trimethylpentane,1,2-epoxycyclohexane, 1,2-epoxycyclooctane,1,2-epoxy-4-cyclohexylpentane, 1,2-epoxyoctadecane, 1,2-epoxyeicosane,styrene oxide, 1,2-epoxytriacontane, 1,2-epoxy-2-cyclohexylbutane,3,4-epoxy-3,4-diethylhexane, 1,2-epoxy-2-(para-tolyl)butane, and2,3-epoxy-3-methyl-2-benzylpentane; and wherein said cyclic anhydride isselected from maleic anhydride, succinic anhydride, glutaric anhydride,phthalic anhydride, 3-methylphthalic anhydride, 4-methylphthalicanhydride, cis-hexahydrophthalic anhydride, trans-hexahydrophthalicanhydride, hexahydro-4-methylphthalic anhydride,cis-1,2,3,6-tetrahydrophthalic anhydride, citraconic anhydride,dl-camphoric anhydride, 3-methylglutaric anhydride, methylsuccinicanhydride, and 2-dodecen-1-ylsuccinic anhydride, and wherein saidorganolithium compound is n-butyllithium, said solvent is cyclohexane,and said mixing of said epoxy compound and said mixing of said cyclicacid anhydride are carried out at a temperature of 80° to 120° C.
 10. Amethod according to claim 9 wherein said carboxy containing polymerconstitutes at least 75 percent of total polymer produced by saidprocess.
 11. A method according to claim 2 wherein said carboxycontaining polymer constitutes 60 to 95 percent of total polymerproduced by said process.
 12. A method according to claim 2 wherein saidcarboxy containing polymer has a 90 to 80 weight percent diene and a 10to 20 weight percent monovinyl substituted aromatic compound content andwherein a molar ratio of said epoxy compound to polymer lithium producedby said polymerization is within the range of 0.8/1 to 2/1 and wherein amolar ratio of said cyclic acid anhydride to said polymer lithium iswithin the range of 0.8/1 to 2/1.
 13. A product produced by the methodof claim
 1. 14. A polymerization process comprising:introducingn-butyllithium initiator into a reaction zone; sequentially introducingstyrene and then butadiene and carrying out polymerization incyclohexane solution; thereafter introducing ethylene oxide or propyleneoxide and mixing the resulting ingredients at a temperature of 100°-120°C.; directly thereafter introducing hexahydro-4-methylphthalic anhydrideand mixing at a temperature of 100°-120° C.; subjecting the resultingcomposition to steam stripping; and recovering a polymer.
 15. A polymerproduced by the method of claim 14.